Certain motor vehicles contain column-type electric power steering systems. The electric power steering system provides torque assist to the steering shaft of a vehicle via an electric motor and a worm/worm gear reduction mechanism. The worm/worm gear reduction mechanism is interposed between the output shaft and the motor to obtain an appropriate steering speed as well as sufficient steering assistance in the course of transmission of the rotational force from the motor to the output shaft.
When the motor vehicle is traveling over a less-than-smooth road surface, a certain amount of road impact energy is created at the points at which the steerable wheels contact the road surface. The road impact energy travels through the tires, wheels and linkage, through the rack and pinion gear, and through the column mounted electric power steering system. The road impact energy causes high bi-directional acceleration of system components, which creates audible noise, commonly known as rattle. While not indicative of a defect in the system, such rattle oftentimes proves to be an annoyance to the occupants of the motor vehicle.
A method and apparatus for reducing rattle and increasing road feel at a steerable wheel in a vehicle. When road impact energy is transmitted through a transmission medium, which includes a column mounted electric power steering system, an audible noise may be generated throughout a steering system of a vehicle. Interrupting the transmission medium and absorbing the road impact energy through the steering system reduces the audible noise in the steering system and increases the road feel at the steerable wheel of the vehicle.
A column assist isolation system includes a sleeve disposed at a housing of an electric power steering system, a first bushing disposed at a first end of the sleeve, and a second bushing disposed at a second end of the sleeve. Both the first bushing and the second bushing include compliant materials.